Brake mechanism for lifting-jacks



M. J. HARKLES S.

A BRAKE MECHANISM FOR LIFTING JACKS- APPLICATION FILED OCT 27, 1919. 1,396,955, Patented Nov. 15, 1921 kgg/ 4 M. J. HARKLESS. BRAKE MECHANISM FOR UFTING JACKS.

- APPLICATION FILED 01:121. 1919. Patented NOV. 1921.

2 SHEETSSHE1,2. 669 v 6 0 a yz fzyflzz w mwim UNITED STATES PATENT OFFICE.

MERI- J. HARKLESS, OF HARVEY, ILLINOIS, ASISIGHOR. TO THE BUDA. COMPANY, A

CORPORATION OF ILLINOIS.

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Specification of Letters Patent.

Patented Nov. 15, 1921.

Application filed October 27, iota. Serial in. 333,484.

To all whomv it may concern;

Be it known that I, Minn. J. HARKLESS, a citizen; of the United States, and a resident of Harvey, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Brake Mechanismfor Lifting-Jacks, of which the following is a full, clear, and exact. description, reference being had to the accompanying drawings, forming a partof this specification.

My present invention relates to. improvements in a manually operated brake. mechanism for lifting jacks, and is in the nature of: a division of a co-pending application for Letters Patent of the United States, Serial Number 333,486. It) has reference more particularly to lifting jacks of the self-lowering type, such as is described and set forth in said co-pending' application, wherein the positive stop means shown is composed of two pivoted braking members normally spring hold to grip a revoluble memberto prevent rotation of its shaft, said members releasablie against the springs to permit shaft rotation by means of a manually operated lever. One of the salient ob: jects of this invention is the provision of means designed to cooperate with said pivoted brake members whereby 1n one pos1- tion of the lever said shaft is held against involuntary rotary movement in the event of spring failure and a further object of my invention is to provide means for locking said lever in such position.

These, together with such other objects as may hereinafterappear, or are intadent to my invention, I attain by means of a construction illustrated in preferred form in the accompanying drawings, wherein:

Figure 1 represents a new in vertical'section of a portion of a jack gear casing illustrating, in side elevation, a brake mechanism constructed in accordance with my invention; i

Fig. 2 is a section on the line Q -Q of ig. 3 is a horizontal sectional view talren through such mechanism along the cutting line 3-3 of Fig. 2; and

Fig. 4 represents a. view in perspective of the manually operated lever when locked.

In the drawings:

The roferencenumcrals 5 and 6 designate a pair of connected inner and outer fixed plates or suppoitspmvided with bearings 7 and 8 for a rotary shaft 9 which in turn imparts similar movement to a spur gear 10 mounted on said shaft. The outer plate 6 may constitute the removable part of a gear casing 11, and both plates may be desirably connected together by the headed securing elements 12 and associated as a unit to the casing by the cap screws 13.

In the co-pendingapplication to which reference has above been made, this spur gear 10 is a member of an automatic governor control. for governing the descent of the ack, the other members of which are not here disclosed as they form no part of the present invention.

Terminally pivoted to the casing or outer plate 6 by means of pivot insdd are a pal-r of brake members '15 having hubs 16 through which said pins extend and promated with curved central portions 17 normally grlpping an outwardly extending an nular brake drum 18 formed on the web of the gear 10 to hold the shaft 9 against rotation. These members have end portions 19 positioned in substantial parallelism and provided on their outer faces with oppositely disposed and. staggered inclined surfaces 20, 21 and abutments 22.

The reference numeral 23 designates a pair of opposed coil springs the outerends of which are engaged by abutments 24; which are integral with supports 25 mounted in the plate 5, while their inner ends engage the abutments 22. In this manner the normal braked relation of the gear 10 and shaft 9 is maintained.

Means are provided to separate, at will, the end portions 19. of the members 15 and thereby release the latter against the pres sure exerted by the springs to permit rotation of the shaft, and such means, in the present instance, takes the form of an actuating spindle 26 having a bearing in a hub portion 28 provided in the outer plate 6, and being provided at its outer exposed end with a manually operated lever 29 and at its inner end with a cam 31. This lever occupies the left hand position shown in Fig. 4, adjacent the lever guard 30, when the. brake members are frictionally engaged with the brake drum 18 to hold the gear 10 against rotary movement, and when the cam is in its inoperative position as indicated in Fig. 2.

The shaft is further provided with an arm 32 whose end portions 33, 34 are formed with abutments 35 and 36 normally engaging the inclined faces 20 and 21. Obviously, if the lever is pressed toward the guard 30 these abutments will serve to hold the brake members in their operative gripping relation with the drum 18 even were the springs, for any adventitious reason, to fail. With the jack under load any such failure might in an ordinary jack result in accident or in the case of a self-lowering jack in the involuntary lowering of the load, unless prevented by the positive means provided in the shape of the arm 32 and abutments 35 and 36.

In order to relieve the operator of the burden of holding the lever in its left hand position so that the abutments 35 and 36 may press against the surfaces 20 and 21 in the event of spring failure, I provide a locking means for said lever in the form of a spring-pressed pawl A comprising a stop head 37 and a rod 38 slidable in a chamber 39 formed within the plate 6. Housed within this chamber is a spring 40 coiled about the rod 38 and positioned therein to yieldingly maintain the head 37 in its normal advanced position (Fig. 1), the outer beveled portion 371 of the head normally projecting beyond the outer face of the plate 6 to be positioned in the path of a flange 291 formed on the back face of the lever 29 to lock the latter in its emergency position as will be readily understood from an inspection of Fig. 4. i

A slight pressureexerted against the projecting beveled head portion 371 permits of the throwing of the lever in a right hand direction in order to release the braking pressure on the shaft. Return movement of the leverto its left hand position is assured by means of the springs 23 acting against the brake members when the lever is thus positioned and thereby rotary movement of the shaft is prevented, and being locked it follows that the abutments 35 and 36 are in a position to maintain the frictional relation of the brake members with the drum 18 should any spring failure occur. Obviously movement of the lever in a right hand direction operates to throw the arm and its abutments out of contact with the surfaces 20 and 21, just exactly as such movement coincidentally serves to actuate the cam 31 which effects the spreading of the brake members on their pivots to release the brake.

1. In braking mechanism for llfting acks, the combination of a support, a revoluble member carried in said support and provided with an annular braking surface, a pair of braking members pivoted to sald support and provided with aspring meansfor yieldingly maintaining said members in frictional contact with said surface a shaft carried by said support in parallelism with the axis of said revoluble member and provided with an actuating lever and a cam for separating the ends of said braking members upon actuation of the lever and an arm on said shaft provided with means co-acting with said ends for positively holding said braking members against said surface, said arm being releasable to take up an inoperative position upon actuation of the lever.

2. In braking mechanism for lifting jacks, the combination of a support, a revoluble member carried in said support and provided with an annular braking surface, a pair of braking members pivoted to said support and provided with a spring means for yieldingly maintaining said members in frictional contact with said surface, a shaft carried by said support in parallelism with the axis of said revoluble member and provided with an actuating lever and a cam for separating the ends of said braking members upon actuation of the lever, an arm on said shaft provided with means co-acting with said ends for positively holding said braking members against said surface, said arm being releasable to take up an inoperative position upon actuation of the lever, and a spring-pressed stop member adapted to yieldingly hold the lever against involuntary acutating movement.

3. In braking mechanism for lifting jacks, the combination of a support, a revoluble member carried in said support and provided with an annular braking surface, a pair of braking members pivoted to said support and provided with a spring means for yieldingly maintaining said members in frictional contact with said surface. a shaft carried by said support in parallelism with the axis of said revoluble member and provided with an actuating lever and a cam for separating the ends of said braking members upon actuation of the lever, an arm on said shaft provided with means eo-acting with said ends for positively holding said braking members against said surface, said arm releasable to take up an inoperative position upon actuation of the lever. and a stop member projecting through said support into the path of lever movement to hold the lever against involuntary actuating movement, said stop member being capable of being retracted in said support to permit of lever movement and the separation of said braking members.

4. In a brake mechanism for jacks, the combination of a support, a rotatable member mounted therein and provided with an annular braking surface, a pair of brake members mounted on said support in position to embrace said annular braking surface, means for yieldably urging said braking members into engagement with said braking surface, means for moving said members into inoperative position against the force of said yielding means, and means for positively holding said brake members in braking relation with said surface.

5. In a brake mechanism for lifting jacks, the combination of a support, a rotatable brake element mounted thereon, a pair of brake members pivoted on said support in position to embrace said element, springs for normally urging said members into engagement with said element, a shaft, a cam on said shaft for moving said members into inoperative position against the force of said springs, an arm on said shaft, and means carried by said arm for positively forcing said members into braking relation with said element.

6. In a brake mechanism for lifting jacks, the combination of a support, a rotatable brake element mounted thereon, a pair of brake members pivoted on said support, springs for urging said members into engagement with said element, a shaft, a cam on said shaft for moving said members into inoperative relation with respect to said element against the force of said springs, and means carried by said shaft for positively engaging said members with said element.

7. In a brake mechanism for lifting jacks, the combination of a support, a rotatable brake element mounted thereon, a pair of brake members pivoted on said support, springs for urging said members into engagement with said support, a shaft, a cam on said shaft for separating said members against the force of said springs, means oarried by said. shaft for compressing said mem bers against said element, a handle for actuating said shaft, and means for locking said handle against movement to lock said members in engagement with said element.

MERL J. HARKLESS. 

